Thank you ever so kindly, pchelp, for your previous post.
I was beginning to think I'd never get a solution to the problem I was having with this Radeon 9250. And I was complicating matters further by trying to get things to work, running Win 7 on a decrepit Intel D865GBF Motherboard (don't ask, and at least it's got 2gigs of memory) with a reasonably nice Acer P191W monitor that likes things best with a native 1440x900 screen resolution.
Phew!
Aero is turned off, natch, but otherwise things work quite well and the display is tack-sharp with excellent colors. This rig will never be used to play any games, or do much of anything except allow its operator to access their email and the usual ham and eggs of typical documents and photographs opening and closing.
About the only thing I have to add to your post is perhaps a warning of what happened to me when I initially restarted after removing ati2dvag.dll from System32 and placing it on the desktop.
Upon restart, I discovered, to my horror, that I was now down to a four-color display with 600x400 resolution! Went into the Screen Resolution screen, and was further horrified to discover that there were no other display options to choose from.
Yikes!
Went ahead and dropped the file back into System32, as instructed, and nothing changed.
YIKES!
Did another reboot, and still nothing had changed.
YIKES!
And then occurred to me to click on the "Advanced settings" words there, hidden in plain sight, on the control panel Screen Resolution screen. And there, lo and behold, under the Adaptor tab, was a button that said "List All Modes" and when I clicked it, a perfectly lovely list of different display settings was available. So I hit one of the higher ones, but, as it turned out, it still was not the native resolution for this Acer monitor. But no worries, hitting that button somehow broke the logjam down in the bowels of the machine, and the next time I right clicked the desktop and clicked on Screen Resolution, all of the options were right there, ready to go. I had previously downloaded and installed the small Acer utility for this monitor, and it perked right up after having previously been moribund, and it very helpfully pointed me toward the happy land of Preferred screen resolution and ever since, things have been just ticky-boo.
So thanks to you, pchelp, for taking the time to figure this little conundrum out and then post it here, and hopefully my own unworthy contribution may also assist someone, somewhere, someday, who has to make things work on things that don't want to work with our old friend, the Radeon 9250.